Portable fire alarm



Aug. 10, 1948.

Filed July 30, 1947 R. B. THORNTON 2,446,794

PORTABLE FIRE ALARM 2 Sheets-Sheet 1 2w W'jqifi Aug. 10, 1948. R. B. THORNTON PORTABLE FIRE ALARM 2 Sheets-Sheet 2 Filed July 50. 1947 12211822302 Budobfi B. Thoflniozw,

Patented Aug. 10, 1948 UNITED STAIES-BATENT OFFICE ron'ranm ma ALARM Rudolph B. Thornton, Winchester, Mass.

Application July 30, 1947, Serial No. 764,821 1 Claim. (01. 177-311) This invention relates to fire alarms, and is particularly concerned with a portable fire alarm which may be carried from place to place to be used wherever it is deemed expedient.

The invention contemplates the utilization of a thermostatic element which will function to close a circuit to sound the alarm when the temperature at the alarms location has risen to a predetermined degree.

It is appreciated that portable fire alarms operating broadly on the same general principle as my alarm have been made, but the alarms of the prior disclosures have been cumbersome and ill adapted for convenient transportation and use.

Accordingly, the present invention resides in the particular arrangement of the parts which results in a novel, compact, sturdy structure which will have long life. In addition, the utilization of the cover member as the-bell reduces the size and number of parts.

The nature of the invention will be'more particularly understood as the description proceeds with the aid of the accompanyin drawings, in which Fig. 1 is an elevational view of the unit as it would appear hanging on a wall.

Fig. 2 is an elevational view similar to Fig. 1 with the cover broken away to expose the interior mechanism.

Fig. 3 is a view on the line 3-3 of Fig. 2.

Fig. 4 is a section on the line 4-4 of Fig. 2.

Fig. 5 is a section on the line 5-5 of Fig. 2.

Fig. 6 is a section on the line 66 of Fig. 2.

Fig. 7 is a schematic drawing of the electrical circuit.

Referring to Figs. 1 to 6, the alarm comprises a housing 2 which serves not only to cover and protect the bell ringing mechanism but also acts as the bell part of the unit. This cover or bell is secured to an inverted U-shaped support 4 by means of screws 6. The area of engagement between the bell and support 4 is small. Support 4 has feet 8 and 9 preferably spot-welded to a mounting plate Hi. This mounting plate carries all of the electrical and working elements of the unit, which are positioned to be entirely clear of bell 2, but at the same time adequately protected thereby. Since the only connection between hell 2 and plate I0 is support 4, a clear loud bell sound is obtained when the bell is struck by the operating mechanism which will hereinafter be described.

Plate III has two upturned tabs l 2 and I4 which carry the thermostatic switch mechanism. Also mounted on plate III are a pair gfgspring clips I6 2 and N! which rigidly grip a tube 20, ordinarily made of insulating material, in which are positioned in series two dry cells 22 and 24. The bottom contact of cell 22 rests against a spring clip 26 which is grounded to plate I0.

On the edge of plate I 0 opposite the batteries is another upstanding support 28 which carries a 'bell hammer arm 42, having on its end bell hammer 44. This latter member is insulated from arm 42 by the two insulating discs 46. Spring 40 extends in the usual manner as at 48, to be normally in engagement with the upstanding contact 50, which, as shown in Fig. 4, is insulated from the base Ill by the insulation 52.

The top contact 54 of battery 24 is an engagement with conductor 56, which extends through tab l4 and is insulated therefrom by the tubular insulator 58. Conductor 56 is also in engagement with the two spring fingers 60 and 62, which are mounted on tab l2 and insulated therefrom by insulating block 64. Another insulating block 66 separates fingers 60 and 62 from the thermostatic element 68, which is normally separated from contact 62 as shown. Element 68, being preferably a bimetallic strip, bends downwardly to engage finger 62 when the temperature has risen to the predetermined degree,

From thermostatic element 68 leads a wire 10 which connects with one end of coil 32. Another wire I2 leads away from the other end of coil 32 to connect with one end of coil 30. Another wire 14 leads from the other end of coil 30 to the contact 50. Thus, when thermostatic element 68 is in engagement with finger 62, there is completed an electrical circuit as follows: starting with battery 22 through battery 24, conductor 56, fingers B0 and 62, thermostatic element 66, wire 10, coil 32, wire 12, coil 30, wire 14, contact 50, spring 48, support 36, plate l0, and spring 26, back to batery 22.

This closed circuit magnetizes the two cores l6 and 18 to draw hammer arm 42 to the left, as viewed in Fig. 2, thereby breaking the circuit between contact 48 and contact 50. This demagnetizes cores l6 and I8 and spring 40 causes contacts 4B and 50 to come into engagement again. Thus the bell hammer vibrates continuously so long as thermostatic element 68 remains in contact with finger 62.

From the foregoing description it can be seen that an alarm will be given immediately upon the temperature rising to the predetermined degree. The alarm will continue to sound until the unit is removed to a cooler place or the circuit is broken.

It will be noted in the several figures, and particularly in Fig. 2, that there are provided two auxiliary connectors, 80 and 82, which may conveniently be connected by wires 84 and 86 to a small push button switch (not shown). If such push button switch is included, it provides an easy way of closing the circuit by hand for the purpose of testing the condition of the batteries and the operativeness of the electrical circuit. Ordinarily, however, it will be suflicient to test the circuit by pressing thermostatic element 68 against finger 62.

While the invention has been illustrated by reference to a preferred form, it is to be understood that it is not to be limited thereby, but only by the appended claim.

I claim:

A portable fire alarm, comprising a mounting plate, a centrally located support on said mounting plate, a cover acting as a bell mounted on said support and having only a small area in contact with said support, said cover being of such dimensions as to completely conceal said mounting plate when viewed from the cover side, the rear said mounting plate extending beyond the rear edge of said cover whereby said plate may be nositioned against a surface without said surface interfering with said cover, a pair of upturned tabs at one end of said plate, one of said tabs supporting a contact adapted to be engaged by a battery and the other of said tabs supporting a thermostatically operable element, a battery positioned on said plate on one side of said support, a bellringing mechanism attached to said plate on the other side of said support in a position where the hammer of said mechanism will, when in operation, hit said cover. and electrical circuit connectin the aforesaid parts whereby, when said circuit is closed by the operation of said thermostatic element, said alarm will ring.

RUDOLPH B. THORNTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 436,961 Upton et a1 Sept. 23, 1890 1,239,850 Vogel Sept. 11, 1917 2,220,979 Swanson Nov. 12, 1940 FOREIGN PATENTS Number Country Date 8,777 Great Britain 1890 

